Just to add to that, it looks like some manufacturers have already pushed out the new microcode alongside the recent ME fixes.

I flashed my Skylake laptop a few days ago, and now I'm on microcode rev 0xc2 (versus 0xba in the latest Intel tarball). CPUID output suggests IBRS support (according to [1]).

[1] https://patchwork.kernel.org/patch/10147547/